The present invention generally relates to improving lithography by using a coating containing a cleaving compound to trim resist features. In particular, the present invention relates to using a stabilization coating and irradiation to double the number of developed resist structures.
In the semiconductor industry, there is a continuing trend toward higher device densities. To achieve these high densities there has been and continues to be efforts toward scaling down the device dimensions on semiconductor wafers. In order to accomplish such high device packing density, smaller and smaller features sizes are required. This includes the width and spacing of interconnecting lines and the surface geometry such as corners and edges of various features. Since numerous interconnecting lines are typically present on a semiconductor wafer, the trend toward higher device densities is a notable concern.
The requirement of small features (and close spacing between adjacent features) requires high resolution photolithographic processes. In general, lithography refers to processes for pattern transfer between various media. It is a technique used for integrated circuit fabrication in which a silicon slice, the wafer, is coated uniformly with a radiation-sensitive film, the resist, and an exposing source (such as optical light, X-rays, or an electron beam) illuminates selected areas of the surface through an intervening master template, the photomask, for a particular pattern. The lithographic coating is generally a radiation-sensitized coating suitable for receiving a projected image of the subject pattern. Once the image is projected, it is indelibly formed in the coating. The projected image may be either a negative or a positive of the subject pattern. Exposure of the coating through the photomask causes a chemical transformation in the exposed areas of the coating thereby making the image area either more or less soluble (depending on the coating) in a particular solvent developer. The more soluble areas are removed in the developing process to leave the pattern image in the coating as less soluble polymer.
Projection lithography is a powerful and essential tool for microelectronics processing. However, lithography is not without limitations. Patterning features having dimensions of about 0.25 xcexcm or less with acceptable resolution is difficult at best, and impossible in some circumstances. Patterning small features with a high degree of critical dimension control is also very difficult. Procedures that increase resolution, improved critical dimension control, and provide small features are therefore desired.
The present invention provides a chemical feature doubling processes, methods of forming sub-lithographic features, and methods of treating patterned resists. The present invention also provides size reduced resist features that are particularly useful for subsequent semiconductor processing procedures. The methods of forming sub-lithographic features and treating patterned resists are conducted in a controllable manner whereby the number of resist features is doubled and thus the spacing of resist features on a substrate may be decreased.
In one embodiment, the present invention relates to a method of treating a patterned resist involving providing the patterned resist having a first number of structural features, the patterned resist comprising an acid catalyzed polymer; contacting a coating containing a coating material, at least one basic compound, a photoacid generator, and a dye with the patterned resist; irradiating the coated patterned resist; permitting a deprotection region to form within an inner portion of the patterned resist; and removing the coating and the deprotection region to provide a second number of patterned resist structural features, wherein the first number is smaller than the second number.
In another embodiment, the present invention relates to a method of decreasing the spacing between patterned resist features involving depositing a coating over the patterned resist features having a first spacing therebetween, the coating comprising at least a basic compound, a photoacid generator, a light absorbing dye, and a coating material, the patterned resist feature comprising a polymer having an acid labile pendent group; irradiating the coated patterned resist features, thereby forming a deprotected region in the inner portions of the patterned resist features; and removing the coating and the deprotected region thereby providing patterned resist features having a second spacing therebetween, wherein the second spacing is smaller than the first spacing.
In yet another embodiment, the present invention relates to a method of making a sub-lithographic structure, involving patterning a chemically amplified resist so as to have lithographic structures; contacting coating with the patterned chemically amplified resist, the coating comprising an amine or a hydroxide compound, a photoacid generator, a light absorbing dye, and a coating material; irradiating the coated patterned chemically amplified resist; removing the coating from the patterned chemically amplified resist; and contacting the patterned chemically amplified resist with an aqueous alkaline developer to provide the sub-lithographic structure.